Coating high temperature parts with polymer

Abstract

Devices and methods described herein operate with high temperature parts, such as heated metal parts obtained from a furnace via a conveyer. For example, in an embodiment, heated parts are coated with a coating solution by spraying the solution onto the parts without a quenching process. Methods and devices in embodiments allow cutting the volume of coating solution required for coating parts. Further, by not quenching the heated parts, heat remaining in the parts after coating process can be utilized for subsequent heat-requiring steps. Further, dispensing flow rate of the coating solution can be adjusted by a pump, thereby controlling coating density and temperature of the parts. Coated parts can dry without forced air, additional heat, or additional time. This allows a secondary operation shortly after the coating process, for which a dry surface is required.

1 . An apparatus for coating heated metal parts without quenching, comprising:
 a conveyor of metal parts from an oven, the metal parts having mean temperatures between 300 and 500 degrees Fahrenheit;   a source of aqueous polymer solution;   a dispenser fluidically connected to the polymer solution, the dispenser positioned to coat at least most of the outside surfaces of the metal parts; and a pump for moving the aqueous polymer solution through the dispenser at a controlled flow rate; wherein   the pump is controlled to dispense polymer solution onto the heated metal parts at a rate that cools the metal parts less than  100  degrees Fahrenheit until a dry state.   
   
   
       2 . The apparatus of  claim 1 , wherein the aqueous polymer solution comprises a polyanionic polymer at a concentration of at least 2% weight/volume and a volatile base. 
   
   
       3 . The apparatus of  claim 2 , wherein the polymer comprises acetoacetoxy-type functional moieties and the polymer solution further comprises amine-functional moieties. 
   
   
       4 . The apparatus of  claim 2 , wherein the volatile base is selected from the group consisting of dimethylamino hydroxypropane, amino methyl propanol, dimethyl amino methyl propanol, dimethyl amino ethanol, diethyl amino ethanol, morpholine, polyethyleneamine and triethanolamine. 
   
   
       5 . The apparatus of  claim 1 , further comprising a catch basin located below the dispenser and positioned to collect overspray. 
   
   
       6 . The apparatus of  claim 1 , further comprising a second, non-aqueous solvent based polymer solution and a second dispenser fluidically connected to the second polymer solution and positioned to dispense the second polymer onto the metal parts after they have dried. 
   
   
       7 . The apparatus of  claim 1 , wherein the dispenser is a spray curtain. 
   
   
       8 . The apparatus of  claim 1 , wherein the aqueous polymer solution comprises a volatile base that buffer the solution with a pKa below 9. 
   
   
       9 . The apparatus of  claim 1 , wherein the metal parts have mean temperatures between 300 and 500 degrees Fahrenheit. 
   
   
       10 . The apparatus of  claim 1 , wherein the aqueous polymer solution comprises a stryrine acrylic polymer and a volatile base. 
   
   
       11 . A method for coating heated metal parts without quenching them, comprising:
 providing hot metal parts at mean temperatures between 300 and 700 degrees Fahrenheit via a conveyor;   spraying the metal parts with a coating solution comprising an aqueous polymer and a volatile base; and   allowing the parts to air dry, where   the spray density and conveyor movement allows cooling the parts by less than 50 degrees Fahrenheit while air drying.   
   
   
       12 . The method of  claim 11 , wherein the hot metal parts are provided at mean temperatures of between 400 and 550 degrees Fahrenheit. 
   
   
       13 . The method of  claim 11 , wherein the coating solution comprises a polyanionic polymer at a weight to volume ratio of between 0.5 to 15 percent, and a volatile base. 
   
   
       14 . The method of  claim 13 , wherein the volatile base is a non-ammonia buffer compound with a pKa less than pH 10. 
   
   
       15 . The method of  claim 11 , wherein the spraying step comprises dropping the parts through a waterfall curtain or ring tube. 
   
   
       16 . The method of  claim 15 , wherein the waterfall curtain is positioned at an intersection between a first conveyor that brings the metal parts from a furnace and a second conveyor positioned horizontally below the first conveyor. 
   
   
       17 . The method of  claim 11 , wherein the conveyor speed and the
 spraying volume are manually controlled individually.   
   
   
       18 . The method of  claim 11 , wherein the conveyor comprises two parallel conveyors with a small gap between them that is small enough to prevent the parts from falling out. 
   
   
       19 . The method of  claim 18 , wherein the gap size is between 0.1 and 0.5 times the mean part diameter size, with respect to the horizontal movement axis of the part on the conveyor. 
   
   
       20 . The method of  claim 11 , further comprising a computer with a stored program that controls at least conveyor speed or spraying volume rate, and which accepts user input to select an optimum speed or volume rate that corresponds with a part type.